cannot understand commission

i thought IB was the cheapest commussion structure. but my statement does not state so. i buy 150 shares and commissioni s 1$. i buy 800 shares the commission is 4$.
does that mean if i buy 2000 shares the commission is 10$, its a ripoff.

Read the info. When you look at the unbundled rate be sure to add in all the other fees to IB's commission rate to determine your final cost. IB's bundled rate is "all in" and there are no further costs.

Don't forget there is a 'Maximum per order' which will prevent the commission from being larger than 0.5% of the trade value plus fees. This is good for those trading low dollar stocks. Imagine buying 1,000,000 shares of an OTC stock that is only $0.005 per share. The total trade value is only $5,000.00 and the 0.5% cap on commission keeps you from paying more than the trade is worth!